BARE BONES
I really enjoy working out a design by drawing it out.
Your sketch made in blue ball-point pen on A4 is great for thinking on the page, but I guarantee you’re likely to get a fright when you see things actually drawn out to scale.
So even if you’re not looking for full plans to submit to council, it’s worth it to get to grips with actual sizes. Also super helpful for space planning and making sure your sofa will fit.
Plans are how you talk to the builder. I’ve seen this be forgotten many times.
The more detailed your plans are, the more you can think about how all the pieces will fit together. This takes more time, but is almost always worth it to avoid costly oopsies later on when both the client and contractor are fed up and just want to get the project finished.
MY SOAPBOX
I’m old enough to have started my training by actually drawing plans with pen on paper. I still think there’s something really beautiful to drawing by hand, though who has the time? At least I can still use skeuomorphic computer programs that mimic the feeling of drawing a line by hand. And nobody has to look at my wobbly handwriting.
I have a strong aversion to software that combines into one both 3D modelling and 2D plans. It’s almost always very rigid in the design language it encourages, while being sloppy when it comes to detailing. I’ve had to clean up SO MANY 3D models with overlapping geometry. I hate it.